At present, HSS supports both LTE (E-UTRAN) access and Non-3GPP access in accordance with 3GPP Evolved Packet System (EPS) specifications, which provides for mechanisms for subscription, authentication and mobility management.
In accordance with 3GPP TS 23.402 chapter 12 “Interactions between HSS and AAA Server”, a 3GPP AAA can be used in Non-3GPP access scenarios to authenticate and authorize a UE connecting from a Non-3GPP access network (e.g. CDMA2000) to an EPC network via the SWx interface towards HSS. In this respect, 3GPP TS 29.273 chapter 8 “SWx description” describes the interface SWx. These 3GPP specifications are incorporated by reference in its entirety.
FIG. 1 shows a non-roaming architecture within EPS for non-3GPP accesses. As shown in FIG. 1, a HSS 110 is connected to a 3GPP AAA server 120 via an interface SWx. On the other hand, those accesses from non-3GPP networks, such as one from UE 150a, trusted non-3GPP IP access 150b and untrusted non-3GPP IP access 150c are routed to the 3GPP AAA server 120 via a number of interfaces, e.g., S6b, SWm, SWa and STa.
Conventionally through the SWx interface, 3GPP AAA retrieves security and authorization information stored in HSS. The HSS keeps track of the AAA Identity currently serving a user in the Non-3GPP access network. SWx is also used to update the HSS with PDN-GW Identity information to facilitate handover (HO) between 3GPP and Non-3GPP accesses.
When a HSS suffers a restart or data reload after failure, this HSS may lose dynamic data such as 3GPP AAA registration information for a number of users, or any PDN-GW identity used as mobility anchor for user sessions in 3GPP and Non-3GPP accesses.
In this situation, the HSS does not have valid information to identify subscribers and 3GPP AAA servers serving the subscribers, and this can cause severe consequences. A first consequence may be that the HSS can not update user contexts stored in the 3GPP AAA server or De-Register users due to administrative reasons. A second consequence may be a rejection by such HSS of subscriber profile retrieval, PDN GW Identity updates and/or Deregistration initiated from a 3GPP AAA server, especially, where there is no information or obsolete information stored in such HSS. A third consequence may be that UE authentication would be allowed if no binding information is stored, whilst there may be other 3GPP AAA server already serving the user. A still fourth consequence may be that there may be multiple 3GPP AAA servers serving a same user and this makes the situation being even worse.
However, in the Non-3GPP Access scenario, there is no fault recovery procedure between a 3GPP AAA server and a HSS when a HSS failure happens, and this will cause problems for 3GPP AAA during the UE attach, detach or handover.